1. Field of the Invention
The present invention relates to the area of mobile platforms used in micro machine tools, in particular to a dual-toggle-type mobile platform structure with an optimal design, a small footprint, a large stroke and a small feed resolution difference.
2. Description of the Related Art
Precision manufacturing machinery is an essential basis for industrial developments as well as a major key for industrial upgrades. Taiwan is one of the major global machine tools producing countries, and faces a trend of miniaturizing various kinds of electronic, communication, optic, medical, and related products, and a strict requirement of manufacturing precisions, so that machine tools for the manufacture must be upgraded constantly to meet different industrial requirements.
In general, the requirement of machine tools is nothing more than the manufacturing precision, and major errors affecting the precision of the machine tools are mainly divided into the following four types:
(1) Geometric errors mainly caused by the manufacture and installation of the machine tools.
(2) Kinematic errors mainly caused by a defective transmission mechanism.
(3) Thermal induced errors mainly caused by an increased temperature of the main shaft or a change of ambient temperature.
(4) Dynamic errors mainly caused by dynamic loads.
In general, a mobile platform of a serial mobile platform structure used for manufacturing has a feed resolution varied with the precision of a driving system (or servo system) of a server, and thus the feed resolution of the mobile platform is limited by the precision of the servo system, and a toggle-type mobile platform structure drives the mobile platform by one or more link rods and amplifies the feed resolution of the servo system by a trigonometric and geometric relation between the link rods, so to have the advantages of a low cost and a high precision, and the feed resolution of the mobile platform is no longer limited by the precision of the servo system.
In the motion of a single-toggle-type mobile platform, the feed resolution of the mobile platform changes with the angle of toggle link rods, and the feed resolution varies with a big difference, so that a dual-toggle-type mobile platform comprising two sets of serially connected single-toggle-type mobile platforms can reduce the difference of the feed resolutions of the mobile platform significantly. Compared with the structure of a single-toggle-type mobile platform or a serial mobile platform, the dual-toggle-type mobile platform can meet the low-cost and high-precision requirements. With reference to FIG. 1 for a schematic view of the structure of a conventional dual-toggle-type mobile platform, the dual-toggle-type mobile platform 1 comprises a base 11, a motor 12, a ball screw 13, a linear slide 14, a first toggle link rod 15, a second toggle link rod 16, a guide rail 17 and a work platform 18. Wherein, the motor 12 is installed on a side of the base 11; the ball screw 13 has an end coupled to the motor 12 and a screw platform 131 disposed on the ball screw 13; the linear slide 14 is installed on the base 11 and disposed perpendicular to the ball screw 13 and has a moving block 141 disposed on the linear slide 14, and a first fixed connecting point 1411 and a second fixed connecting point 1412 defined on the moving block 141, and wherein the first fixed connecting point 1411 and the second fixed connecting point 1412 are arranged next to one another can be connected to define a connecting line which is perpendicular to the linear slide 14. The first toggle link rod 15 has a first connecting portion 151 and a second connecting portion 152, wherein the first connecting portion 151 is coupled to the screw platform 131, and the second connecting portion 152 is coupled to the first fixed connecting point 1411. The second toggle link rod 16 has a third connecting portion 161 and a fourth connecting portion 162, wherein the third connecting portion 161 is coupled to the second fixed connecting point 1412, and a pair of the guide rails 17 are disposed on the base 11 and separately perpendicular to the linear slide 14 and parallel to the ball screw 13. The work platform 18 is movably installed on the guide rail 17 and coupled to the fourth connecting portion 162. The working angles of the first toggle link rod 15 and the second toggle link rod 16 are complementary to each other to maintain a mild change of the feed resolution of the motor 12, so as to provide the advantage of a small feed resolution difference.
In the mechanical design of a single-toggle-type mobile platform or a dual-toggle-type mobile platform, the length of the toggle link rods must be increased, so that the work platform 18 can meet the working stroke requirement, but the length of the toggle link rods is a main factor affecting the overall size of a machine. Since different lengths of the toggle link rods will affect the overall footprint of the machine, the increased length of the toggle link rods can provide a larger displacement in a fixed working angle range, yet the distance between the ball screw 13 and the mobile platform 18 is affected, so that the size of the base 11 will be increased. Compared with the serial mobile platform structure capable of producing the same working stroke, the volume and footprint of this machine is increased by approximately 2.5 to 3 times. It is an important subject for designers and manufacturers of the related industry to design a dual-toggle-type mobile platform structure that can meet the requirements of small space, large stroke, and small resolution difference.
In view of the problems of the conventional mobile platforms, the inventor of the present invention develops a dual-toggle-type mobile platform structure that changes the way of connecting the toggle link rods and adopts an optimal configuration for the mechanical design, so as to provide a mobile platform having the advantages of small footprint, large stroke and small resolution difference. Actual practices of the novel dual-toggle-type mobile platform structure indicate that its performance can be applied for micro manufacture in the future.